Electron discharge apparatus



:lume 20, 1939. A. L. SAMUEL ELECTRON DISCHARGE APPARATUS Filed July 22, 1937y /NVENTOR A. L .SAMUEL 5V 1 OMI/ Mm@ F/IG. 2

ATTORNEY IPatented June 20, 1939 UNITED STATES ELECTRON DISCHARGE `APPARATUS Arthur L. Samuel, Summit-N. J., assignor to Bell Telephone Laboratories,

Incorporated, New

York, N. Y., a. corporation of New York Application July z2, 1937, lserial No. 155,017

15 Claims.

This invention 4relates to electron discharge apparatus and more particularly to such apparatus especially suitable for the generation and amplification of ultra-high frequency impulses.

One object of this invention is to increase the operating efficiency of electron discharge apparatus.

Another object of this invention is to facilitate the generation and amplification of impulses of extremely short wave-lengths, for example, wavelengths of the order of one meter or less.

A further object of this invention is to simplify the structure of electron discharge apparatus and thereby to reduce the number of component elements thereof.

In one illustrative embodiment of this invention, electron discharge apparatus comprises a pair of spaced cathodes having opposed electron emitting surfaces, and an anode between the cathodes and outside of the peripheries of the electron emitting surfaces thereof. These surfaces may be coated with a material having good secondary emitting properties. During operation of the apparatus, electrons emanating from one of the cathodes flow to and impinge upon the lother cathode and cause the emission of secondary electrons therefrom. These secondary electrons in turn flow toward the rst cathode, impinge thereon and cause'the emission of other secondary electrons therefrom. Inasmuch as each electron impinging upon a cathode causes the release of a plurality of secondary electrons, a repeated electron multiplication occurs at the l cathodes. Eventually some of the electrons between the cathodes are attracted to the anode and constitute an oscillating current.

In accordance with one feature of this invention, the cathodes and the anode have juxtaposed surfaces defining inductances of predetermined magnitudes which together with the interelectrode capacitances provide a. tuned circuit resonantto the frequency at which the apparatus is intended to operate. The cathodes and the anode mayhave other juxtaposed portions forming direct current blocking condensers in the anode-cathode circuit.

In accordance withanother feature of this invention, a thermionic cathode is provided between the two opposed cathodes aforementioned and may be electrically connected thereto at its ends, and means are provided for producing a magnetic field adjacent and parallel to the thermionic cathode. The thermlonic cathode and the anode constitute elements of a magnetron, oscillation of which is initiated by the emission of electrons Y (Cl. Z50-27.5)

from the thermionic cathode. The oscillatory current is augmented by the secondary electrons emitted from the opposed cathodes, these cathodes oscillating substantially in phase becauseof the electrical connection therebetween provided by the thermionic cathode.

The invention and the foregoing and other fea.- tures thereof will be understood more clearly and fully from the following detailed description with reference to the accompanying drawing in which: E Fig. 1 'is an elevational view in perspective of electron discharge apparatus constructed in accordance with this invention, portions thereof being broken away to show the various elements more clearly; v

Fig. 2 is a detail cross-sectional vview `of a modification of the cathodes shown in Fig. 1;

Fig. 3 is an elevational view in cross-section of electron discharge apparatus illustrative of another embodiment of this invention; and

Fig. 4 is a diagrammatic view illustrating the external electrical association of the electrodes of the device shown in Fig. 3.

Referring now to the drawing, the electron discharge device shown in Fig. 1 comprises an enclosing vessel having vitreous end portions I provided with inwardly extending stems Il, and an intermediate metallic portion serving as the anode of the device. The metallic portion includes a cylinder I2 hermetically sealed at its ends to the vitreous portions I0, and an inwardly extending annular flange I3, preferably midway between the ends of the cylinder I2, and having annular arcuate surfaces I4. V

lDisposed on opposite sides of the annular flange I3 are a pair of cathodes, each of which includes a plane surface I5, preferably coated withva material having good secondary electron emitting properties, a cylindrical flange I6 adja- A cent and coaxial with the cylindrical portion I2 of the anode, and annular, substantially semi-cylindrical surfaces I1 coaxial with the arcuate surfaces `I4.l The electron emitting portions I preferably areof smaller diameter than the central aperture in the flange I3 and mounted parallel to and coaxial with each other. Preferably these portions I5 are spaced such a distance that the transit time of an electron flowing therebetween is commensurate with the periodvof the operating frequency of the device.

The cathodes may be supported by rigid rods or leading-in conductors I8 embedded in` the stem I I and threaded into central hubs I9 in the cathodes. Fitted on each of the supports I8 is an insulating disc abutting the corresponding hub Il and locked thereagainst by a stub 2i affixed to the corresponding support Il. The discs 2l are fitted within the cylinder I2 and maintain the cathodes in `cgaxial relation with the anode.

'lhe juxtaposed surfaces Il and II, it will be enclosing vessel of the device, resonant to the frequency at which the'device is to be operated. The cylindrical portions I2 and l of the anode and the cathodes respectively define direct current blocking condensers in the tuned circuits.

During operation of the device, the cathodes may be connected together directly so that they are at substantially the same mean potential. A positive potential is impressed upon the anode as by a source, such vas a battery 22, shown in Fig. 4, connected directly between the anode and the cathodes, the potential being such that the fundamental period of oscillation is the same as theA resonant period of the tuned circuit described heretofore. The anode may be encompassed by a cylindrical electromagnetic coil 23,

which produces a substantially constant, concen- Y trated magnetic field between the surfaces I5 of the cathodes and coaxial therewith.

f When the potential is impressed upon the anode, under one mode of oscillation, the cathode surfaces I5 will be at different instantaneous potentials because of the tuned circuit therebetween. That is to say, when one surface I5 is secondary electrons from the lower surface I5 and these secondary electrons will be attracted to the upper surface I5 and impinge thereon, causing the emission of other secondary electrons. This phenomenon of impinging. electrons and the resultant emission of secondary electrons will be repeated alternately at the surfaces I5 so that 'there will be produced an oscillating electron field between the two cathodes. Because of the coat-I ings on the surfaces I5, each impinging electron will cause the emission of a plurality of secondary lelectrons so that in effect an electron multiplication occurs at each lof the cathodes during each cycle of the operating frequency.

The magnetic eld produced by the coil 23 concentrates the various electron streams owing between the cathodes, along the longitudinal axis of the device so that for several cycles at least the great majority of the electrons pass through the ce tral aperture in the flange Il of the anode. As the electron eld between the cathodes increases, however, some of the electrons are drawn therefrom periodically and iiow to the anode flange I3 and constitute the oscillating current in the anode circuit.

An output or utilization circuit may be coupled magnetically to the internal oscillating circuit of the electron discharge device as by an openend arcane? ed, looped or substantially cylindrical conductor 24 encircling the anode of the device.

As illustrated in Pig. 2, one or both of the cathodes in the device shown in Fig. l may be of theindirectly vheated thermionic type compris- 'ing a heater filament 2l adjacent the emitting portion I5 and encased in an insulating or ceramic material 28 in a recess in the cathode; One of the leading-in conductors 21 for the 4iliament 25 may be connected to the hub Il. which is offset as shown, and the other leading-in conductoxi |28 may be sealed in and extend from the In the embodiment of the invention illustrated in Figs. 3 and 4, a linear cathode 28, for example, a filament of thoriated tungsten, extends between the cathodes I5 and is coaxial therewithl and with the anode flange Il.` The cathode 2l may extend throughcentral apertures 30 in the cathodes I5 and be supported from rigid metallic rods 3|, sealed in the stems 32, by resilient members 33. Preferably the rods 3i are connected electrically to the adjacent support or leading-in conductor by metallic strips or wires 33. As shown in Fig. 4, heating current for the iilamentary cathode may be supplied from a source, such as a battery 34, connected between the'leading-in conductors Il, and the anode may be maintained at a positive potential with respect to all of the cathodes as by a battery 22. A

During operation of the device, the magnetic field produced by-the coil 23, and the potential upon the anode are so adjusted that the cathode 29 and anode constitute a magnetron element, the oscillating frequency of which will be dependent upon the interelectrode capacitances and the inductances formed by the surfaces I1, the inductances and capacitances preferably being made of -such magnitude that the circuit of which they form a part is tuned to the frequency at which the device is intended to operate., The oscillating current will be augmented bythe secondary electrons, emanating from the surfaces I5, generated as described heretofore in connection with Fig. l. Inasmuch as the cathodes I5 are connected directly by the lamentary cathode 28, the electron current emanating therefrom will oscillate substantially in phase and contribute simultaneously to the oscillating current of the magnetron element. i

Although specific embodiments of the invention have been shown and described, it will be understood, of course, that various modications may be made therein withoutl departing from the scope and spirit of this invention 4as defined in the appended claims.

What is claimed is:

1. An electron discharge device comprising an evacuated enclosing vessel, an annular anode and a cathode having an electron emitting portion in cooperative relation with said anode, said anode and said cathode having juxtaposed annular surfaces bounding a substantially toroidal cavity and having portions separate from said surfaces deiining a condenser.

portion, and a second cathode on the other side ci' said portion, said cathodes having opposed parallel electron emitting surfaces, and said anode and said cathodes having juxtaposed surfaces dening inductances which form a resonant circuit with the interelectrode capacitances.

4. An electron discharge device in accordance with claim 3 in which each of said cathodes has a portion cooperating with said anode to form a condenser therewith.

5. An electron discharge device comprising an evacuated enclosing vessel, an anode including a. portion having an aperture therein, and a pair of cathodes on opposite sides of said portion, said cathodes having parallel secondary electron emitting portions in alignment with said aperture, and said anode and said cathodes having juxtaposed surfaces bounding substantially toroidal cavities.

6. An electron discharge device in accordance with claim 5 comprising means for producing a magnetic field between said cathodes. v

7. An electron discharge device in accordance with claim 5 in which said anode and said cathodes have coaxial cylindrical portions dening condensers.

8. An electron discharge device comprising an anode having an opening therein, an elongated cathode extending through said opening, and a pair of cathodes at opposite ends of said elongated cathode and having opposed electron emitting surfaces. n

9. An electron discharge device comprising a cylindrical anode, a linear thermionic cathode coaxial with said anode, and a pair of secondary electron emitting cathodes at opposite ends of said thermionic cathode hand having opposed emitting surfaces. 10. An electron discharge device in accordance with claim 9 comprising means electrically connecting said secondary electron emitting cathodes to saidI thermionic cathode.

11. Anelectron discharge device comprising an anode having an apertured portion, a illamentary cathode in cooperative relation with said anode and extendingthrough the aperture in said portion, and a pair of auxiliary cathodes adjacent opposite ends of said lamentary cathode, said auxiliary cathodes having parallel secondary electron emitting surfaces on opposite sides of said portion and in alignment with the aperture therein.

12. An electron discharge device in accordance with claim 11 comprising means electrically connecting said auxiliary cathodes to said iilamentary cathode, and means for producing a magnetic eld adjacent said lamentary cathode.

13. An electron discharge device comprising an anode having an annular portion, a iilamentary cathode extending through said portion and coaxial therewith, means for producing a magnetic Afield adjacent said cathode and parallel thereto,A and a pair of auxiliary cathodes on opposite sides of said portion and electrically connected to the ends of said fllamentary cathode, said auxiliary cathodes having parallel, opposed secondary electron emitting portions coaxial with said filamentary cathode, and said anode and said auxiliary` cathodes having juxtaposed arcuate surfaces bounding Asubstantially toroidal cavities.

14. An electron discharge device in accordance with claim 13 in which said anode and said auxiliary cathodes have juxtaposed cylindrical portions dening condensers.

15. An electron discharge device comprising an anode having an annular portion, and a pair of cathodes on opposite sides oi' said annular .portion having parallel, opposed electron emitting surfaces in alignment with each other and the aperture in said annular portion, resistance means electrically connecting said cathodes, said anode and said cathodes having portions defining inductances constituting a tuned circuit with the interelectrode capacitances, and said surfaces being spaced a distance such that the transit time of an electron owing therebetween is commensurate with the period of the resonant frequency of said circuit. 

